The stage is set in Italy. Rebecca has been kidnapped! She belongs to one of the most prominent families in the Republic of San Marino and the young woman is the CEO of the Rossellini conglomerate which operates the largest chain of hotels in Italy. Rebecca becomes interested in Lupin, who saves her from this crisis, and the two tie the knot at once...

Additionally, Lupin receives a written challenge from a mysterious person named "The Masked Count" suggesting a contest: who can obtain the "inheritance of Count Cagliostro" first.

(Source: TMS Anime Official YouTube Channel, Anime News Network)